1. Field of the Invention
The present invention relates to a label manufacturing method and a label manufacturing system for manufacturing a label made of a heat sensitive adhesive sheet having a heat sensitive adhesive layer formed on a single side of a sheet-like substrate, which normally exhibits no adhesive properties but develops adhesive properties when being heated.
2. Description of the Related Art
Conventionally, a heat sensitive adhesive sheet having a heat sensitive adhesive layer that develops adhesive properties when being heated has been commercialized. Such a heat sensitive adhesive sheet as described above has advantages that the sheet before being heated can be handled easily because the sheet does not have the adhesive properties and that the heat sensitive adhesive sheet does not need release paper and industrial waste is thus not produced. Further, a label made of the heat sensitive adhesive sheet is attached onto various articles and is used in many fields such as a display like a bar code or the like for a point of sale (POS) of products such as foods, a shipping tag for distribution and delivery, a baggage tag in a hotel or a vehicle, or a display of contents of a bottle, a can, a cartridge or the like.
In general, the heat sensitive adhesive sheet is transported while heating means heats the heat sensitive adhesive layer to develop adhesive properties, whereby a desired label is manufactured. Some of the labels manufactured from the heat sensitive adhesive sheet in a certain use may be formed to include an adhesive portion and a non-adhesive portion disposed in a mixed manner instead of having the adhesive properties in an entire surface thereof. For instance, it is considered that a rim portion of the label is the adhesive portion while an inside portion thereof is the non-adhesive portion. In addition, it is considered that a part of the label, which is cut off and saved as a copy, is the non-adhesive portion. As described above, the adhesive portion that is heated so as to develop the adhesive properties and the non-adhesive portion that is not heated so as not to develop the adhesive properties may be disposed in a mixed manner in one label.
Note that a thermal head that is usually used as a recording head of a thermal printer is used as heating means for heating the heat sensitive adhesive layer of the heat sensitive adhesive sheet in many cases (see Patent Documents JP 2004-243606 A and JP 2004-136972 A). In this case, the heat sensitive adhesive layer of the heat sensitive adhesive sheet is pressed to the thermal head while the heat sensitive adhesive sheet is transported, whereby the entire surface or a part of the surface of the heat sensitive adhesive layer is thermally activated so as to develop adhesive strength. When the thermal head is used, it is relatively easy to dispose a heated part and a non-heated part mixedly in the heat sensitive adhesive layer.
When the heat sensitive adhesive sheet is transported while the heating means is actuated to heat the heat sensitive adhesive layer to be thermally activated as described above, a period of actuating the heating means is determined based on a desired label size. More specifically, operation of the heating means is stopped substantially at the same time when a trailing end portion of the heat sensitive adhesive sheet has passed through a position contacting with the heating means.
However, a mechanical error may occur in operation of a label manufacturing apparatus (a transport error of the heat sensitive adhesive sheet, or the like). For instance, if the trailing end portion of the heat sensitive adhesive sheet reaches the position contacting with the heating means later than a calculated timing in the case where a transporting amount per row of the heat sensitive adhesive sheet has decreased or in other case, the operation of the heating means may be stopped before the trailing end portion of the heat sensitive adhesive sheet reaches the position contacting with the heating means. As a result, the trailing end portion of the heat sensitive adhesive sheet is not heated and is not thermally activated, with the result that the adhesive properties are not developed.
The mechanical error itself is substantially constant within a tolerance, and can be reduced sufficiently by adjusting a heating pattern in accordance with the error before output thereof. However, even if the same adjustment as described above is performed, an unintentional non-adhesive portion may be generated largely in the trailing end portion in a transporting direction of the heat sensitive adhesive sheet. In particular, an error in the transporting amount per row is accumulated while the transporting of the heat sensitive adhesive sheet per row is repeated, and hence a position error of the heat sensitive adhesive sheet at the trailing end portion in the transporting direction is apt to be larger than that at other portion of the heating pattern (portion other than the trailing end portion). In addition, it is difficult to predict the position error because an extent of the position error varies depending on a transport length. Therefore, it is not easy to deal with the position error in advance by adjusting the heating pattern. As a result, if an unintentional non-adhesive portion is generated in the trailing end portion in the transporting direction of the heat sensitive adhesive sheet, a problem may occur that a label made of this heat sensitive adhesive sheet is removed easily after being attached to an article.